Microelectromechanical systems (“MEMS,” hereinafter “MEMS devices”) are used in a wide variety of applications. For example, MEMS devices currently are implemented as microphones to convert audible signals to electrical signals, as gyroscopes to detect pitch angles of airplanes, and as accelerometers to selectively deploy air bags in automobiles. In simplified terms, such MEMS devices typically have a movable structure suspended from a substrate, and associated circuitry that both senses movement of the suspended structure and delivers the sensed movement data to one or more external devices (e.g., an external computer). The external device processes the sensed data to calculate the property being measured (e.g., pitch angle or acceleration).
During production, the structure on a MEMS device commonly is doped so it can cooperate effectively with the circuitry. This process generally involves applying doping material to the top surface of the structure prior to a release step (i.e., the step that frees the structure to move relative to the substrate). When the structure is relatively thick, (e.g., about ten microns or greater), however, the doping material, which was applied to the top surface, may not dope the opposite side of the structure to adequate levels. In addition, it also is very difficult to actually release the structure when it is so thick. If not appropriately doped or released, the MEMS device will not operate properly.